Light-emitting device

ABSTRACT

A light-emitting device includes: a semiconductor laser element; a supporting member located above the semiconductor laser element, the supporting member having a through-hole that allows light emitted from the semiconductor laser element to pass therethrough; a fluorescent member located in the through-hole, the fluorescent member containing a fluorescent material that is excitable by light emitted from the semiconductor laser element so as to emit light having a wavelength different from a wavelength of the light emitted from the semiconductor laser element; and a light-transmissive heat dissipating member including: a base portion, and a projecting portion projecting from the base portion into the through-hole. An upper surface of the projecting portion of the heat dissipating member is bonded to a lower surface of the fluorescent member. An upper surface of the base portion of the heat dissipating member is bonded to a lower surface of the supporting member.

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims priority to Japanese Patent ApplicationNo. 2016-109252, filed on May 31, 2016, the disclosure of which ishereby incorporated by reference in its entirety.

BACKGROUND

The present disclosure relates to a light-emitting device.

A semiconductor light-emitting device configured to extract lightemitted from a semiconductor light-emitting element through alight-extracting window on which a light-transmissive film is attachedhas been described (see Japanese Unexamined Patent ApplicationPublication No. H11-087778). The light-transmissive film is coated witha fluorescent substance. Alternatively, the fluorescent substances aredispersed in the light-transmissive film (see paragraph 0255 in JapaneseUnexamined Patent Application Publication No. H11-087778).

SUMMARY

During operation of a semiconductor light-emitting device, a fluorescentsubstance is irradiated with light from the semiconductor light-emittingelement, which allows the fluorescent substance to generate heat.Conventional semiconductor light-emitting devices may not have astructure considering such heat generation, and accordingly, suchsemiconductor light-emitting devices may not achieve higher output.

In one embodiment, a light-emitting device includes a semiconductorlaser element, a supporting member located above the semiconductor laserelement, the supporting member having a through-hole that allows lightemitted from the semiconductor laser element to pass therethrough, afluorescent member located in the through-hole, the fluorescent membercontaining a fluorescent material excitable by light emitted from thesemiconductor laser element so as to emit light having a wavelengthdifferent from a wavelength of light emitted from the semiconductorlaser element, and a light-transmissive heat dissipating memberincluding a base portion and a projecting portion projecting from thebase portion into the through-hole, the through-hole is tapered so as towiden in an upward direction, an upper surface of the projecting portionof the heat-dissipating member bonded to a lower surface of thefluorescent member, and an upper surface of the base portion of the heatdissipating member bonded to a lower surface of the supporting member.

With the configuration above, both of the heat dissipation from afluorescent member and the light extraction efficiency of alight-emitting device can be improved, so that high output of thelight-emitting device can be effectively achieved.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a schematic cross-sectional view of a light-emitting deviceaccording to a first embodiment.

FIG. 1B is a schematic enlarged view of a supporting member, afluorescent member, and a heat dissipating member in FIG. 1A.

FIG. 2A is a schematic cross-sectional view of a light-emitting deviceaccording to a second embodiment.

FIG. 2B is a schematic enlarged view of a supporting member, thefluorescent member, and a heat dissipating member in FIG. 2A.

FIG. 3A is a schematic cross-sectional view of a light-emitting deviceaccording to a third embodiment.

FIG. 3B is a schematic enlarged view of the supporting member, afluorescent member, and the heat dissipating member in FIG. 3A.

DETAILED DESCRIPTION Light-Emitting Device 1 According to FirstEmbodiment

FIG. 1A is a schematic cross-sectional view of a light-emitting device 1according to a first embodiment. FIG. 1B is a schematic enlarged view ofa supporting member 40, a fluorescent member 50, and a heat dissipatingmember 60 in FIG. 1A. As shown in FIG. 1A and FIG. 1B, thelight-emitting device 1 includes a semiconductor laser element 10, thesupporting member 40, the fluorescent member 50, and thelight-transmissive heat dissipating member 60. The supporting member 40is disposed above the semiconductor laser element 10 and defines athrough-hole Y that allows light emitted from the semiconductor laserelement 10 to pass through. The fluorescent member 50 is disposed in thethrough-hole Y and contains a fluorescent material that is excited bylight from the semiconductor laser element 10 and emit light having awavelength different from the wavelength of light from the semiconductorlaser element 10 upon the excitation. The heat dissipating member 60includes a base portion 62 and a projecting portion 64 projecting fromthe base portion 62 into the through-hole Y. The through-hole Y broadensupward. The upper surface of the projecting portion 64 of the heatdissipating member 60 is bonded to the lower surface of the fluorescentmember 50. The upper surface of the base portion 62 of the heatdissipating member 60 is bonded to a lower surface of the supportingmember 40.

With the present embodiment, both the heat dissipation from thefluorescent member 50 and the light extraction efficiency of thelight-emitting device 1 can be improved, so that high output of thelight-emitting device 1 can be effectively achieved. That is,improvement in the heat dissipation from the fluorescent member 50allows for irradiation of the fluorescent member 50 with more intenselight, so that output of the light-emitting device 1 can be enhanced.Further, improvement in the light extraction efficiency of thelight-emitting device 1 can increase the amount of light extracted fromthe light-emitting device 1, so that output of the light-emitting device1 can be enhanced. Accordingly, higher output of the light-emittingdevice 1 can be effectively achieved by improving both the heatdissipation from the fluorescent member 50 and the light extractionefficiency of the light-emitting device 1. Additional details will bedescribed below.

Semiconductor Laser Element 10

For the semiconductor laser element 10, for example, a semiconductorlaser element having a peak lasing wavelength in a range of 420 nm to470 nm can be used. Improvement in the heat dissipation from thefluorescent member 50 as in the present embodiment allows thelight-emitting device 1 to operate with stable optical properties evenin the case where the fluorescent member 50 is irradiated withhigh-power laser light having output of, for example, 2.0 W or more,preferably in a range of 2.0 W to 5.0 W.

The semiconductor laser element 10 is disposed laterally to a heatsink20. For the heatsink 20, a material with good thermal conductivity, suchas copper, aluminum, and brass, is preferably used so that the heatdissipation from the fluorescent member 50 can be further improved. Theheatsink 20 is fixed to a plate-shaped stem 21. The semiconductor laserelement 10 is electrically connected to lead terminals 22 viaelectrically-conductive members such as wires.

Surrounding Member 30

A surrounding member 30 surrounds the semiconductor laser element 10 anddefines an opening X through which light emitted from the semiconductorlaser element 10 can pass. The lower surface of the heat dissipatingmember 60 is in contact with the upper surface of the surrounding member30, and the lower surface of the supporting member 40 is bonded to theupper surface of the surrounding member 30 via the heat dissipatingmember 60. A heat-dissipating path that allows heat from the supportingmember 40 to be transferred to the heat dissipating member 60 andfurther to the surrounding member 30 is provided, so that heatdissipation from the fluorescent member 50 is further improved. Amaterial such as stainless steel and Kovar® (nickel—cobalt ferrousalloy) can be used for the surrounding member 30.

Supporting Member 40

The supporting member 40 is disposed above the semiconductor laserelement 10. For the supporting member 40, for example, a ceramic with ahigh reflectance, or a metal member having a reflective film on theinner wall of the through-hole Y can be used. Using such a material asthe supporting member 40 allows for facilitating reflection of lightfrom the fluorescent member 50 on the inner wall of the through-hole Y,so that the light extraction efficiency of the light-emitting device 1can be improved.

The supporting member 40 defines the through-hole Y through which lightfrom the semiconductor laser element 10 can pass. The through-hole Y hasa shape in which a width increases upward. With such a shape, forexample, a portion of light that has been reflected in the fluorescentmember 50 can be easily reflected upward by the inner wall of thethrough-hole Y, so that light extraction efficiency of thelight-emitting device 1 can be further improved.

Fluorescent Member 50

The fluorescent member 50 is disposed in the through-hole Y. Thus, theinner wall of the through-hole Y is located at a lateral side of thefluorescent member 50. With the inner wall of the through-hole Y locatedat a lateral side of the fluorescent member 50, light from thefluorescent member 50 can be reflected on the inner wall of thethrough-hole Y, thereby improving the light extraction efficiency of thelight-emitting device 1.

The fluorescent member 50 contains the fluorescent material to beexcited by light emitted from the semiconductor laser element 10 and toemit light having a wavelength different from the wavelength of lightemitted from the semiconductor laser element 10. More specifically, forexample, a member containing the fluorescent material in a base membersuch as sintered body made of a ceramic material and alight-transmissive resin can be used for the fluorescent member 50. Inparticular, using a ceramic sintered body as the base member allows forreducing deformation of the fluorescent member 50 due to heat generatedby the fluorescent material, so that optical properties of thelight-emitting device 1 can be stabilized. Accordingly, the fluorescentmember 50 can be irradiated with even more intense light, thereby moreeffectively achieving higher output of the light-emitting device 1.Examples of the ceramic material include aluminum oxide (Al₂O₃),zirconium oxide (ZrO₂), and titanium oxide (TiO₂).

Examples of the fluorescent material include yttrium-aluminum-garnetfluorescent materials (YAG fluorescent materials),lutetium-aluminum-garnet fluorescent materials (LAG fluorescentmaterials), terbium-aluminum-garnet fluorescent materials (TAGfluorescent materials), and SiAlON fluorescent materials. Thesematerials can be used singly or in combination.

The fluorescent member 50 may contain a light-scattering member such assilicon oxide (SiO₂), aluminum oxide (Al₂O₃), zirconium oxide (ZrO₂), ortitanium oxide (TiO₂). With the fluorescent member 50 containing thelight-scattering member, light emitted from the semiconductor laserelement 10 can be scattered within the fluorescent member 50, so thatunevenness in color of light extracted from the light-emitting device 1can be reduced. The light-scattering member has, for example, a granularshape.

Heat Dissipating Member 60

The heat dissipating member 60 includes the base portion 62 and theprojecting portion 64 projecting from the base portion 62 into thethrough-hole Y and is light-transmissive to light from the semiconductorlaser element 10. Sapphire or magnesia, having light-transmissiveproperty, can be used for the heat dissipating member 60. Sapphire,which has relatively high heat dissipation performance, is preferablyused. The heat dissipating member 60 can have a thickness in a range ofabout 200 μm to 1,000 μm. With the thickness of the heat dissipatingmember 60 of 200 μm or greater, the heat dissipation performance of theheat dissipating member 60 can be enhanced, so that the heat dissipationfrom the fluorescent member 50 can be further enhanced. With thethickness of the heat dissipating member 60 of 1,000 μm or smaller,lateral propagation of light through the heat dissipating member 60 canbe reduced, so that light extraction efficiency of the light-emittingdevice 1 can be further enhanced.

The upper surface of the projecting portion 64 is bonded to the lowersurface of the fluorescent member 50. The base portion 62 is bonded tothe lower surface of the supporting member 40. Herein, the bondingsurface between the upper surface of the projecting portion 64 and thelower surface of the fluorescent member 5 is referred to as a firstbonding surface A, and the bonding surface between the base portion 62and the lower surface of the supporting member 40 is referred to as asecond bonding surface B. As described above, with a heat-dissipatingpath (heat-dissipating path across the first bonding surface A) throughwhich heat from the fluorescent member 50 is directly transferred to theheat dissipating member 60 and a heat-dissipating path (heat-dissipatingpath across the second bonding surface B) through which heat from thefluorescent member 50 is indirectly transferred to the heat dissipatingmember 60 via the supporting member 40, the heat dissipation from thefluorescent member 50 can be improved. The lower surface of thefluorescent member 50 particularly easily generates heat by beingirradiated with light emitted from the semiconductor laser element 10,and thus providing the heat-dissipating path across the first bondingsurface A allows for effectively improving heat dissipation from thefluorescent member 50.

In the present embodiment, the heat dissipating member 60 includes theprojecting portion 64, and the upper surface of the projecting portion64 is bonded to the lower surface of the fluorescent member 50. Withthis arrangement, light traveling downward from the fluorescent member50 is more easily reflected by the inner wall of the through-hole Y thanin the case where the heat dissipating member 60 is flat, and a portionof light reflected on the inner wall of the through-hole Y is morelikely to travel upward. In the present embodiment, light extractionefficiency of the light-emitting device 1 can be increased in thismanner.

A dielectric multilayer film that reflects light in a specificwavelength range may be disposed on the lower surface of the heatdissipating member 60 to improve the light extraction efficiency of thelight-emitting device 1. For example, a film that serves to transmitlight in a wavelength range of light emitted from the semiconductorlaser element 10 and to reflect light in a wavelength range of lightemitted from the fluorescent member 50 can be used for the dielectricmultilayer film. With such a dielectric multilayer film on the lowersurface of the heat dissipating member 60, light traveling toward thelower surface of the heat dissipating member 60 can be reflected upwardin the through-hole Y. Accordingly, the light extraction efficiency ofthe light-emitting device 1 can be further improved.

Light-Emitting Device 2 According to Second Embodiment

FIG. 2A is a schematic cross-sectional view of a light-emitting device 2according to a second embodiment.

FIG. 2B is a schematic enlarged view of a supporting member 40, thefluorescent member 50, and a heat dissipating member 60 in FIG. 2A. Asshown in FIG. 2A and FIG. 2B, the light-emitting device 2 differs fromthe light-emitting device 1 according to the first embodiment in thatthe second bonding surface B of the light-emitting device 2 has anirregularity in a cross-sectional view while the second bonding surfaceB of the light-emitting device 1 according to the first embodiment has asubstantially linear geometry in a cross-sectional view. In the secondembodiment, the bonding area (i.e., area of the second bonding surfaceB) between the base portion 62 and the lower surface of the supportingmember 40 can be increased compared with the case where the secondbonding surface B has a linear geometry in a cross-sectional view.Accordingly, heat can be more effectively released through theheat-dissipating path (heat-dissipating path across the second bondingsurface B) through which heat from the fluorescent member 50 isindirectly transferred to the heat dissipating member 60 via thesupporting member 40, so that heat dissipation from the fluorescentmember 50 can be further improved.

Light-Emitting Device 3 According to Third Embodiment

FIG. 3A is a schematic cross-sectional view of a light-emitting device 3according to a third embodiment.

FIG. 3B is a schematic enlarged view of the supporting member 40, afluorescent member 50, and the heat dissipating member 60 in FIG. 3A. Asshown in FIG. 3A and FIG. 3B, the light-emitting device 3 differs fromthe light-emitting device 1 according to the first embodiment in thatthe fluorescent member 50 includes a first fluorescent member 52 bondedto the upper surface of the projecting portion 64, and a secondfluorescent member 54 having a lateral surface supported by the innerwall of the through-hole Y and having a lower surface that includes aportion bonded to the first fluorescent member 52. Also, thelight-emitting device 3 differs from the light-emitting device 1 in thata low-refractive-index portion 70 having a refractive index smaller thanthe refractive index of the first fluorescent member 52 is present at alateral side of the first fluorescent member 52, in the through-hole Y.The low-refractive-index portion 70 has a refractive index smaller thanthe refractive index of the first fluorescent member 52, preferablysmaller than both of the refractive index of the supporting member 40and the refractive index of the first fluorescent member 52. Therefractive index of the first fluorescent member 52 herein is therefractive index of a member mainly exposed on the surface of thefluorescent member 52. The low-refractive-index portion 70 ispreferably, for example, air.

With the low-refractive-index portion 70 having a refractive indexsmaller than the refractive index of the first fluorescent member 52 ata lateral side of the first fluorescent member 52, total reflection onthe interface between the first fluorescent member 52 and thelow-refractive-index portion 70 can be facilitated. Accordingly, lighttraveling from inside of the first fluorescent member 52 toward theinner wall of the through-hole Y can be reduced, so that lightextraction efficiency of the light-emitting device 1 can be furtherimproved. In the case where a ceramic material or the like is used forthe supporting member 40, the low-refractive-index portion 70 preferablyhas a refractive index even smaller than the refractive index of thesupporting member 40. With this arrangement, the inner wall of thethrough-hole Y allows light traveling from the low-refractive-indexportion 70 to be reflected toward the supporting member 40. Accordingly,light entering the supporting member 40 can be reduced, so that leakageof light out of the light-emitting device 1 can be further reduced.

The present embodiment can preferably apply to the case where thesupporting member 40 is made of a member having a relatively smallreflectance, such as a ceramic material, and can also preferably applyto the case where the supporting member 40 is made of a member having arelatively large reflectance, such as a metal material. That is, a metalmaterial has a reflectance greater than the reflectance of a ceramic,but a surface of the metal material easily absorbs light in the casewhere the fluorescent member 50 is in contact with the metal materialunlike the case where the fluorescent member 50 is spaced from the metalmaterial. However, even in this case, with the low-refractive-indexportion 70 having a refractive index smaller than the refractive indexof the supporting member 40, decrease in the light extraction efficiencyof the light-emitting device 1 can be prevented.

In the present embodiment, the low-refractive-index portion 70 ispresent at a lateral side of the first fluorescent member 52, thelateral surface of the second fluorescent member 54 is bonded to theinner wall of the through-hole Y, and a portion of the lower surface ofthe second fluorescent member 54 is bonded to the upper surface of thefirst fluorescent member. With this arrangement, the first fluorescentmember 52 can be fixed between the lower surface of the secondfluorescent member 54 and the upper surface of the heat dissipatingmember 60. Accordingly, even in the case where the first fluorescentmember 52 has a high melting point and thus is difficult to befusion-bonded to the inner wall of the through-hole Y, fixing the secondfluorescent member 54 to the inner wall of the through-hole Y byfusion-bonding allows the first fluorescent member 52 to be disposed inthe through-hole Y.

A ceramic containing a fluorescent-material is preferably used for thefirst fluorescent member 52, and a glass containing a fluorescentmaterial is preferably used for the second fluorescent member 54. Withthis constitution, the first fluorescent member 52 and the secondfluorescent member 54 can be fixed by disposing the second fluorescentmember 54 above the first fluorescent member 52 and fusion-bonding thesecond fluorescent member 54 to the upper surface of the firstfluorescent member 52 and the inner wall of the through-hole Y. Further,using a ceramic containing a fluorescent-material, which has good heatresistance, for the first fluorescent member 52, which is initiallyirradiated with light from the semiconductor laser element 10, allowsthe second fluorescent member 54 to contain a fluorescent materialhaving, for example, poor heat resistance. In the fusion bonding, thefirst fluorescent member 52 and the second fluorescent member 54 areheated at a temperature at which the second fluorescent member 54containing a glass is melted to the degree that enables fusion bondingand the first fluorescent member 52 containing a ceramic is not meltedto the degree that enables fusion bonding. The heating is performed at,for example, about 850° C. Performing heating at this temperature allowsthe first fluorescent member 52 and the second fluorescent member 54 tobe fixed in the through-hole Y while reducing damage to the fluorescentmaterials due to heat.

The first fluorescent member 52 may contain a fluorescent material thatemits light having a wavelength different from that of light emittedfrom a fluorescent material of the second fluorescent member 54. Withthis arrangement, color of light extracted from the light-emittingdevice 3 can be adjusted. For example, by using a semiconductor laserelement for emitting blue light for the semiconductor laser element 10,a fluorescent member containing a fluorescent material that emits yellowlight for the first fluorescent member 52, and a fluorescent membercontaining a fluorescent material that emits red light for the secondfluorescent member 54, white light can be extracted from thelight-emitting device 3.

The first to third embodiments have been described above, but thepresent invention is not limited to the described embodiments.

What is claimed is:
 1. A light-emitting device comprising: asemiconductor laser element; a supporting member located above thesemiconductor laser element, the supporting member having a through-holethat allows light emitted from the semiconductor laser element to passtherethrough; a fluorescent member located in the through-hole, thefluorescent member containing a fluorescent material that is excitableby light emitted from the semiconductor laser element so as to emitlight having a wavelength different from a wavelength of the lightemitted from the semiconductor laser element; and a light-transmissiveheat dissipating member comprising: a base portion, and a projectingportion projecting from the base portion into the through-hole; whereinthe through-hole is tapered so as to widen in an upward direction,wherein an upper surface of the projecting portion of the heatdissipating member is bonded to a lower surface of the fluorescentmember, and wherein an upper surface of the base portion of the heatdissipating member is bonded to a lower surface of the supportingmember.
 2. The light-emitting device according to claim 1, furthercomprising a low-refractive-index portion having a refractive indexsmaller than a refractive index of the fluorescent member, thelow-refractive-index portion being present in the through-hole at alateral side of the fluorescent member.
 3. The light-emitting deviceaccording to claim 2, wherein the low-refractive-index portion is an airfilled space.
 4. The light-emitting device according to claim 2, whereinthe fluorescent member comprises: a first fluorescent member bonded tothe upper surface of the projecting portion; and a second fluorescentmember having: a lateral surface supported by an inner wall of thethrough-hole, and a lower surface including a portion bonded to thefirst fluorescent member, and wherein the low-refractive-index portionis present at a lateral side of the first fluorescent member.
 5. Thelight-emitting device according to claim 3, wherein the fluorescentmember comprises: a first fluorescent member bonded to the upper surfaceof the projecting portion; and a second fluorescent member including: alateral surface supported by an inner wall of the through-hole, and alower surface including a portion bonded to the first fluorescentmember, and wherein the low-refractive-index portion is present at alateral side of the first fluorescent member.
 6. The light-emittingdevice according to claim 1, further comprising: a surrounding membersurrounding the semiconductor laser element and having an opening thatallows light emitted from the semiconductor laser element to passtherethrough, wherein the lower surface of the supporting member isbonded to an upper surface of the surrounding member via the heatdissipating member.
 7. The light-emitting device according to claim 4,further comprising: a surrounding member surrounding the semiconductorlaser element and having an opening that allows light emitted from thesemiconductor laser element to pass therethrough, wherein the lowersurface of the supporting member is bonded to an upper surface of thesurrounding member via the heat dissipating member.
 8. Thelight-emitting device according to claim 5, further comprising: asurrounding member surrounding the semiconductor laser element andhaving an opening that allows light emitted from the semiconductor laserelement to pass therethrough, wherein the lower surface of thesupporting member is bonded to an upper surface of the surroundingmember via the heat dissipating member.
 9. The light-emitting deviceaccording to claim 4, wherein: the semiconductor laser element isadapted to emit blue light, the first fluorescent member contains afluorescent material adapted to emit yellow light, and the secondfluorescent member contains a fluorescent material adapted to emit redlight.
 10. The light-emitting device according to claim 5, wherein thesemiconductor laser element is adapted to emit blue light, the firstfluorescent member contains a fluorescent material adapted to emityellow light, and the second fluorescent member contains a fluorescentmaterial adapted to emit red light.
 11. The light-emitting deviceaccording to claim 4, wherein the first fluorescent member comprises aceramic containing a fluorescent material.
 12. The light-emitting deviceaccording to claim 5, wherein the first fluorescent member comprises aceramic containing a fluorescent material.
 13. The light-emitting deviceaccording to claim 9, wherein the first fluorescent member comprises aceramic containing a fluorescent material.
 14. The light-emitting deviceaccording to claim 10, wherein the first fluorescent member comprises aceramic containing a fluorescent material.
 15. The light-emitting deviceaccording to claim 4, wherein the second fluorescent member comprises aglass containing a fluorescent material.
 16. The light-emitting deviceaccording to claim 5, wherein the second fluorescent member comprises aglass containing a fluorescent material.
 17. The light-emitting deviceaccording to claim 9, wherein the second fluorescent member comprises aglass containing a fluorescent material.
 18. The light-emitting deviceaccording to claim 10, wherein the second fluorescent member comprises aglass containing a fluorescent material.
 19. The light-emitting deviceaccording to claim 1, wherein the upper surface of the base portion ofthe heat dissipating member comprises a plurality of projecting portionsat a region where the upper surface of the base portion of the heatdissipating member is bonded to the lower surface of the supportingmember.
 20. The light-emitting device according to claim 1, wherein anupper surface of the fluorescent member and an upper surface of thesupporting member are in a common plane.